Women's Risk for a Certain Skin Cancer Varies by Geography

THURSDAY, March 13 (HealthDay News) -- An American woman's risk of developing the skin cancer called squamous cell carcinoma appears to increase if she lives in areas where UV radiation is high, such as in the South, a new study found.

The risk of developing another type of skin cancer, basal cell carcinoma, appears to be only moderately affected by living in areas with high UV (ultraviolet) radiation. And the chance of developing melanoma, the deadliest form of skin cancer, is not significantly affected by where you live, the researchers said.

"There's an increased risk of skin cancer in general, as you know, from North to South," said lead researcher Dr. Abrar A. Qureshi, of the Department of Dermatology at the Channing Laboratory of Brigham and Women's Hospital and Harvard Medical School. "So for people living in areas where there is more sun around, the risk of skin cancer is higher, as we've known for decades."

"But what we found was that squamous cell carcinoma was very much related to the North-South difference," Qureshi added. "Women living in the South had a twofold increased risk of developing squamous cell carcinoma, compared with women living in the North."

However, there was no statistically significant difference for developing melanoma, whether women lived in the North or the South, Qureshi said. "We're not saying that melanoma risk doesn't increase with sun exposure, but compared to women living in the North, women in the South did not have a significantly increased risk of melanoma," he said.

The findings were published in the March 10 issue of the Archives of Internal Medicine.

Squamous cell carcinoma is the second most common form of skin cancer, with more than 250,000 new cases diagnosed each year in the United States. Most squamous cell cancers aren't serious, particularly if they're diagnosed and treated promptly. But later diagnoses can mean the cancers are harder to treat and can cause disfigurement. A small number of cases can be potentially fatal, according to The Skin Cancer Foundation.

For the new study, Qureshi's team collected data at 84,836 women who took part in the Nurses' Health Study. The women lived in different parts of the United States with different levels of UV exposure.

Over the 18 years of the study, 420 women developed melanoma, 863 developed squamous cell carcinoma, and 8,215 developed basal cell carcinoma.

The researchers found that women living in areas with medium UV exposure had a 47 percent increased risk of developing squamous cell carcinoma. Women living in areas where UV exposure was high had a 90 percent greater risk of developing squamous cell carcinoma.

Qureshi said it's not clear why there are differences in risk for different types of skin cancer. "The question is, is melanoma more a disease of genetics as well as exposure to the sun," he said. "It could be more of a genetic disease than squamous cell carcinoma -- that's really the question."

It's also not clear if the same risk factors affect men, Qureshi said, adding that he and his colleagues are examining that question now. He speculated that they will find the same relationship for the various types of skin cancer among men.

One skin cancer expert advises people to protect themselves from the sun, no matter where they live.

"We have a slogan of the American Cancer Society -- slip, slop, slap," said Dr. Martin A. Weinstock, a professor of dermatology at Brown University and a spokesman for the American Cancer Society. "Slip on a shirt, slop on the sunscreen and slap on a hat. That's the advice when you're out in the sun to protect yourself from the damage that leads to skin cancer, no matter where you live."